Low dose estrogen plus calcium have been shown to prevent spinal bone loss in early postmenopausal women and calcium plus vitamin D have been shown to prevent hip and other non-spinal fractures in women living in long-term care communities. This project is a pilot study to evaluate the use of calcium and low dose estrogen in healthy community-dwelling older women. The overall aim of this project is to study the interactive effects of calcium and estrogen on biochemical markers of bone turnover in older women over a 6 month period. The specific aims are: 1) to examine the effect of a 12-week course of low dose estrogen or elemental calcium plus vitamin D on biochemical markers of bone turnover in women aged 70 or older; 2) to examine changes in markers of bone turnover with the addition of calcium and vitamin D to the estrogen group and of low does estrogen to the calcium group for an additional 12 weeks; 3) to examine bone turnover 12 weeks after treatment is discontinued; 4) to examine the change in parathyroid hormone levels with the various treatment combinations. The long-term goal is to find an effective, well-tolerated regimen for the prevention and treatment of osteoporosis in women more than 20 years past menopause. All patients are now enrolled in this study and data collection is ongoing.